1. Field of the Invention
The invention relates to a longitudinal adjustment device of a motor vehicle seat, comprising:                stationary bottom rail connectable with a motor vehicle,        seat rail connectable with the motor vehicle seat and longitudinally displaceably supported on the bottom rail between a front and a rear end position.        
2. Description of Related Art
Longitudinal adjustment devices of the initially mentioned type serve to arrange a vehicle seat on a floor assembly of a motor vehicle in a longitudinally displaceable manner. The seat rail connectable to the vehicle seat is longitudinally displaceably supported by the bottom rail connectable to the vehicle floor, so that adjustment of the vehicle seat between a front and a rear position is carried out by adjusting the seat rail between the associated front and rear end positions. The rails of a longitudinal adjustment device are only in contact in guiding areas by means of suitable sliding and/or rolling bodies and are otherwise spaced from each other.
In the case of a crash and the attendant accelerations, it is necessary for the seat rail to be reliably arranged on the bottom rail so that the tensile forces acting on the seat rail due to the crash are reliably transferred to the bottom rail. In particular if a seatbelt lock is arranged on the seat rail, increased acceleration forces act on the seat rail in the case of a crash, the intensity of which also depends on the position of the seat rail with respect to the bottom rail, whereby the highest loads occur if the seat rail is arranged in the area of its rear end position. To guarantee the safety function of the vehicle seat, it must be prevented as far as possible in each seat position that the two rails separate due to the applied loads, for example tear apart in the manner of a zip fastener.
Prior art longitudinal adjustment devices of the initially mentioned type have a U-shaped cross section to achieve a resistance against separation or tearing apart of the rails, wherein the free ends in the cross section of the rails are configured in such a manner that they are in hooked engagement. To achieve sufficient tear resistance for all positions of the seat rail with respect to the bottom rail it is necessary, however, to design the seat rail and the bottom rail under consideration of the highest loads to be expected, whereby the load situation in the case where the seat rail is arranged in the area of the rear end position is to be considered, in particular, since in this position particularly high acceleration forces act on the seat rail of the longitudinal adjustment device in the case of a crash.
In view of the above, it is the object of the present invention to provide a longitudinal adjustment device which protects the seat rail in the area of its rear end position to the greatest possible extent against crash-induced displacement with respect to the bottom rail.
The invention achieves the object by a longitudinal adjustment device having the features of claim 1. Advantageous embodiments of the invention are the subject matter of the dependent claims.